The pursuit for new materials to form the basis for future energy-efficient electronics has
brought forward transition-metal oxides that offer a broad range of potentially coexisting
functionalities. Ferroelectric oxides distinguished by the presence of a non-volatile electric
polarization that can be switched by an electric field are especially promising for the
development of novel electronic devices with reduced power consumption. Despite
having found countless commercial applications owing to their concomitant piezo- and
pyroelectric properties, the integration of ferroelectric oxides into next-generation
memory and logic devices is however, still facing difficulties. Notably, when prepared in
the form of technologically relevant thin films and heterostructures achieving a
deterministic arrangement of domains - the basic functional entities of ferroelectric
materials are rendered challenging by the competing effects of various interactions, such
as strain, electrostatic, and defect chemistry. In our work, we pave the way toward the
design of tailored ferroelectric domain configurations in epitaxial thin films by tracking and
controlling domains at the point of their emergence – during thin-film growth. With the
direct in-situ access to the functional property of ferroelectrics using non-linear optics we
manage to unravel the mechanisms that drive the formation of domains in prototypical
ferroelectric oxides and put forward design strategies to realize highly specialized domain
configurations. In thin films of the archetypal ferroelectrics PbTi03 and Pb(ZrxTi1-x)03 (PZT),
we discover that tensile epitaxial strain induces the formation of in-plane-oriented
domains within an out-of-planeoriented matrix already during thin-film growth [1]. We
further uncover that the epitaxial growth conditions can significantly affect the
concentration of charged defects, which determines the electrostatics during growth
and, hence, provides us with a handle to control the direction of the polarization [2].
Making use of these in-situ observations we then tailor the elastic and electrostatic
boundary conditions in PZT thin to obtain a nanoscale domain configuration exhibiting
nonbinary switching characteristics [3], which ~is essential for applications in brain-inspired
neuromorphic computing. Finally, we explore the use of light as a remote trigger to
optically manipulate the fell'oelectric polarization and find that above-bandgap optical
excitation can strongly alter the charge screening in ferroelectric heterostructures [4].
Depending on the ferroelectric domain configuration this can prompt a transient
modification of the polarization or even non-volatile poling, constituting a major step
toward all-optical control of ferroelectricity.
[1] M.F. Sarott et al. Appl. Phys. Lett. 117, 132901 (2020)
[2] M.F. Sarott et al. Adv. Funct. Mater. 33 . 22 14849 (2023)
[3] M.F. Sarott et al. Nat. Commun . 13, 3159 2022)
[4] M.F. Sarott et al. Adv . Mater. 36, 2312437 (2024)